validate a URL with Javascript

The input can begin with either the text "http" or "file", so the two are grouped together with a | to show that either one or the other value is acceptable. Whether the user is getting the image off of their hard drive or off the Web, the next characters have to be "://", so that's checked for next. Note that each of the forward slashes must be escaped individually (that's what the two instances of \/ are, escaped forward slashes), because forward slashes are regular expression special characters.

After that, nearly anything goes, so \S+ is used to signify that one or more nonwhite space characters follow. Then there's another required forward slash (again escaped) to separate the domain from the file name, and then another \S+ to handle the file name.

The file name needs to end with a period and then either "gif" or "jpg". The period is escaped, and the two suffixes are grouped together to test for either.

After the regular expression, the modifier i is used, to allow the user input to be either upper- or lowercase. This modifier tells the regular expression not to be case-sensitive.

good tuts. I like JS it's client scripting and useful for my work

I have used that code & that's excellently working. I have checked that that's working perfectly.